The present invention is directed to continuous processing methods of photographic film and more specifically to a positive drive transport system for automatically processing lengths and sheets of all types of film and paper.
It is a complex problem to transport a length of film, having a delicate emulsion layer, through the various stages of a developing process.
One of the primary problems experienced in continuous movement processors is bromide drag. Most of the prior art today transport the film by driven rollers held against each other by spring action. As the film passes through the rollers, a squeegee action takes place causing the bromide salts to build up behind the rollers, creating what is known in the trade as "bromide drag". Another serious problem with solid rollers is the build up of silver and other deposits on the rollers which must be removed and cleaned periodically. Solid rollers require a complex spring tensioning arrangement holding one roller against the other to maintain the close tolerances that are necessary.
Another prior art method utilizes solid rollers in combination with woven plastic belts. This system has a streaking problem on the film, due to the belt pressure, and includes a complex apparatus to handle the distortion and stretch of the belts.